446 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



wires. At Saarbrtick it has been found advantaojeous to 

 use a drum of larger diameter than is usual with iron wire, 

 owing, it is presumed, to the fact that steel breaks more 

 readily than iron after it has passed the limit of elasticity. 

 5 0, XLVIIL, 376. 



SUBMERGED CHAIN FOR TOWING BOATS. 



The remarkable success attending the novel system of 

 river navigation, introduced for nearly the whole length of 

 the Elbe River, of towing boats by the aid of a chain sub- 

 merged in the channel, has led to its introduction upon the 

 tributaries of that river. The data furnished by its opera- 

 tion for several years warrant the conclusion that this mode 

 of interior navigation possesses great economical advantages, 

 not only especially as compared with railroads, but also as 

 compared with other modes of towing. By the former meth- 

 ods of towing, the necessity for the reduction of the resist- 

 ance to a minimum led to the building of boats of large size, 

 regardless of the disadvantages connected with them, such 

 as the greater difficulty of obtaining full freight from point 

 to point, uncertainty of running at all stages of water, etc. 

 But besides the reduction of the size of boats allowed by the 

 new system, it is also probable that it will be found applica- 

 ble in cases where the current has been found too stroncr to 

 render navigation practicable by the old method, since a 

 boat towing by means of a firmly anchored chain passing 

 over it is much more nearly independent of the current. 

 34 C, II., 14. 



WIRE ROPES OF PHOSPHOR-BRONZE. 



On account of the higher absolute tenacity and power of 

 resisting torsion possessed by phosphor-bronze wire of cer- 

 tain kinds over that of iron or steel, its advantageous ap- 

 plication in the manufacture of wire ropes for mines was 

 anticipated. The employment of such ropes for several years 

 in England, Belgium, and Westphalia has so completely 

 substantiated the theoretical calculation that their use is 

 rapidly becoming more general. Their first cost, it is true, 

 is greater than of those of iron or steel, but, on the other 

 hand, they afford much greater security, last at least seven 

 times as long as those of steel, and, when unfit for use, the 



